Sensitive light and smoke detecting device with memory system

ABSTRACT

This invention discloses a novel sensitive light and smoke detecting device using a photoelectric element connected in series with a parallel circuit of a discharge tube and a resistance. The decrease in resistance of the photoconductor by reason of an incoming small amount of light dimly lights said discharge tube by increasing the divided current of the parallel circuit and the resulting radiating light from the discharge tube further reduces the resistance of the photoconductor until both photo-electric element and discharge tube mutually react to the fullest extent whereby the discharge tube provides a positive optical feed back to the photoconductor to denote the presence of light and smoke. The circuit provides a signal even after removal of the initially detected light or smoke. The small amount of initial light may be furnished by a dimly lit pilot lamp which is secluded by a wall between the photoconductor and the discharge tube but light can reach the photoconductor by reflection of small amount of incoming smoke and initiate action of the device of this invention.

United States Patent Saito 1 1 May 16, 1972 [54] SENSITIVE LIGHT AND SMOKE 3,034,011 5/1962 Nisbet et al ..315/151 DETECTING DEVICE WITH NIEMORY 3,213,441 10/1965 Shook ..3 15/ 151 SYSTEM 3,233,781 2/1966 Grubbs ..250/218 1 3,376,425 4/1968 Kraus et a1 ..250/218 [72] Inventor: Shinji Saito, 1-306, Maita-cho, Minamiku, Yokohama, Japan Primary Examiner-John Kominski Filed Nov 23 1970 Attorney-Watson, Cole, Grindle & Watson [21] Appl. No.: 91,782 [57] ABSTRACT Relmed us. Application Data This invention discloses a novel sensitive light and smoke detecting device using a photoelectric element connected in sel Continuation-impart 0f ries with a parallel circuit of a discharge tube and a resistance. 1968, abandoned. The decrease in resistance of the photoconductor by reason of an incoming small amount of light dimly lights said discharge [30] Foreign Application Priority Data tube by increasing the divided current of the parallel circuit t and the resulting radiating light from the discharge tube Oct. 25, 1967 Japan ..42/68326 further reduces the resismnce of the photoconductor um both photo-electric element and discharge tube mutually react [52] U.S.Cl ..315/151,250/205,2354%f2128 to the fullest extent whereby the discharge tube provides a I 5 l 1 Int Cl Gosh 17/10 positive optical feed back to the photoconductor to denote the I presence oflight and Smoke The circuit provides a Signal even [58] Field of Search ..340/228,250/2;)l55/2l1581, after removal of the initially detected light or Smoke. The small amount of initial light may be furnished by a dimly lit 56] Reterences Cited pilot lamp which is secluded by a wall between the photoconductor and the discharge tube but light can reach the photoconductor by reflection of small amount of incoming UNITED STATES PATENTS smoke and initiate action of the device of this invention. 2,386,320 10/1945 Kott ..250/205 8/1958 Gridley ..250/205 4 Claims, 2 Drawing Figures FIG? INVENTOR ATTORNEYS SENSITIVE LIGHT AND SMOKE DETECTING DEVICE WITH MEMORY SYSTEM This is a continuation-in-part application of my co-pending application Ser. No. 785,835, filed Oct. 18, 1968, and now abandoned. v

This invention relates to a sensitive light and smoke detecting device which is capable of detecting extremely small amounts of light and smoke and memorizing the existence of said light and smoke.

The term photoelectric element" as used herein denotes an element such as CdS which has a characteristic of decreasing its electric resistance according to the increase in the amount of light radiation falling upon it. The term smoke" as used herein denotes kinds of line particles floating in the air, gas and even in liquid such as fire smoke, dust of furnaces, fumes of sulphuric acid, waste of carbide in water and other nuisances existing in pollution problems. Formerly, photoelectric elements (such as cadmium sulfide indicated as CdS hereafter) have been used for detecting light. CdS has, in general, high electric resistance between its terminals when not exposed to light. The method usually used in detecting light through the use of a substance which has high resistance such as CdS, is that voltage is added to the terminal of the circuit where CdS and the resistance are connected in series and the change of resistance of CdS by the light impinging upon it is detected by determining change of voltage between the terminals of the resistance. However, in this method, it is very difiicult to detect extremely small amounts of light when the voltage change is small. In such cases electric amplifiers have been used to actuate alarm phones and light indicators. Moreover, other self-holding relays have been necessary to keep the alarm working. Such apparatus entail more expense as well as maintenance and may become sources of trouble.

Therefore, the object of this invention is to provide a sensitive light and smoke detecting device which has an optical amplifying circuit in order to easily detect extremely small amounts of light and smoke even when highly resistant CdS is used.

Another object of this invention is to provide a light and smoke detecting device with a memory system which fulfills a function of remembering the detection of a small amount of li ht.

The other objectives and features of this invention will be apparent with the following specification and drawing.

FIG. 1 is a circuit diagram illustrating the electrical connections between the several elements of the present invention; and

FIG. 2 is a diagrammatic vertical longitudinal section through a device constructed in accordance with the present invention.

In FIG. 1, 1 indicates light flux that is intercepted by photoconductor 4, 2 is the light flux from discharge tube 3. 6 and ll are the terminals of the power source supplying stabilized voltage, and 7 and 8 are the terminals of resistance which divides the current in photoconductor 4 and the discharge tube 3. Resistance 12 provides the means from which the output signal is taken, and 9 and 10 are the output terminals.

The operation of this invention can be explained as follows. Between the terminals 6 and l l, a certain operating voltage is applied from the power source. The voltage change between the detecting terminals 9 and 10 is read when input light flux 1 impinges upon photoconductor 4.

When there is no light input ray, the resistance of the photoconductor is high, and the voltage at the junction of resistance 5, photoconductor 4 and discharge tube 3 is finely adjusted slightly lower than the firing potential of the discharge tube. In this case, as the discharge tube is not conductive, current does not run through the detecting resistance 12 and the voltage between 9 and 10 is close to zero. If input light flux l, which is preferably provided by a dimly lit lamp 13 secluded by a wall 14 (FIG. 2) mounted between lamp l3 and photoelectric element 4 reaches the Iphotoconductor by virtue of reflection from a small amount 0 incoming smoke, the resistance of the photoconductor 4 is reduced and the voltage between 6 and 7 decreases while the voltage between 7 and 8 increases by the same amount that the voltage between terminals 6 and 7 decreases. Therefore, the discharge tube 3 is made slightly conductive and its light flux 2 falls upon the photoconductor.

The resistance of the photoconductor is thereby reduced and the voltage at the top of resistor 5 increases. That is, the discharge tube provides a positive feed back, and the current of the discharge tube can be increased to its nominally rated value. The voltage between the terminals 9 and 10 increases from zero by reason of the aforedescribed operation. This phenomena and mechanism can be easily proved by shutting off the feed back light with an opaque substance placed between the photoconductor and the discharge tube and thus an alarm connected with the output will not actuate even when a small amount of light is transmitted to the photoconductor. This is the characteristic difference between conventional detection means and the device of this invention. And when the discharge'tube is conductive, light flux 2 is maintained after the input light flux 1 or the small amount of smoke disappears, and therefore the circuit acts as a type of memory system which records the incidence of input light flux 1.

The efficiency of this invention is indicated by the following considerations. The change of current provided by the detection circuit herein described is approximately 2mA, just about several hundred times the changes (0.02mA) detected through the methods hitherto used.

What is claimed is:

l. A device for detecting particles within a fluid, comprismg;

a housing having a conduit for conveying the fluid,

a light source for lighting said fluid in said conduit,

a photoconductive element for detecting light reflected from said fluid,

an additional light source responsive to the state of said photoconductive element and energized thereby to provide light on said photoconductive element,

said means connected to said photoconductive element for indicating the amount of light reflected from said fluid.

2. A device as in claim 1 further comprising a resistance electrically connected in series with said photo-conductive element and said additional light source is a discharge tube energized by the voltage at the junction of said resistance and said photoconductive element.

3. A device as in claim 2 wherein said means for indicating is an additional resistance connected between said discharge tube and said resistance.

4. A device according to claim 2, said resistance being variable to adapt the device to the detection of suspended materials of differing reflectivities.

l l t 

1. A device for detecting particles within a fluid, comprising; a housing having a conduit for conveying the fluid, a light source for lighting said fluid in said conduit, a photoconductive element for detecting light reflected from said fluid, an additional light source responsive to the state of said photoconductive element and energized thereby to provide light on said photoconductive element, said means connected to said photoconductive element for indicating the amount of light reflected from said fluid.
 2. A device aS in claim 1 further comprising a resistance electrically connected in series with said photo-conductive element and said additional light source is a discharge tube energized by the voltage at the junction of said resistance and said photoconductive element.
 3. A device as in claim 2 wherein said means for indicating is an additional resistance connected between said discharge tube and said resistance.
 4. A device according to claim 2, said resistance being variable to adapt the device to the detection of suspended materials of differing reflectivities. 